The Ernest Henry copper-gold Mineral Resource is the major asset held by Ernest Henry Mining Pty Ltd, comprising A$6.4 billion of contained metal. The case history presented below describing the evolution and evaluation of this resource generally observes best industry practice and is a good example of effective due diligence in the resource delineation and estimation process. Early reconciliation data from mine production confirms the accuracy and validity of the resource estimate, providing valuable assurance to the mine owners.